My $.02 on SRT. I have a PC with a dedicated SSD to cache data and the difference between it and an identical drive in the same system is not noticeable. But to answer your questions...
1 and 2) Yes. Any mSATA SSD should work. However, I think that you are better off getting a 2.5" SATA drive. You can easily transfer it from PC to PC if you need/want to in the future. I personally would say skip caching and get a regular 120GB or 256GB SSD and call it a day.
3) It won't be a problem but from my recollection you can only cache one drive. So you will have to pick drive C or D.

If so,...software question...
I've seen, but can't find, a software that always you to clone you HD to a SDD and during clone process setup the HD as your File/Data Drive.
All in one process. Transfer the OS to the SDD, and sets up your HD as your Data drive. Pretty slick...but I can't find the software.

Again skip the mSATA port. They are usually much slower than an identical 2.5" drive. The other problem is most mSATA drives are only SATA II instead of the newer SATA III standard. Are you thinking of Acronis True Image or Norton Ghost?